Methods for applying wet coating compositions to paper surfaces followed by drying the wet coating with a heated solid polished reflective finish roller for reproducing high gloss finishes in the paper making industry is known. The process is referred to as cast coating or calendaring. The cast coated method employed during paper making produces a high gloss coating image by first applying a wet coating composition to a paper web substrate before it contacts a casting drum (i.e., a heated drum having a highly polished drying surface which creates a glossy image on the paper. In contrast, the present method applies a wet coating composition inline (wet or dry trap) directly onto a smooth, reflective or polished, low energy non-stick surface followed by transferring the coating composition onto the substrate. The cast coated paper, after it is manufactured by the paper mills, is then sold to printers and is used as a high gloss substrate for use in printing applications. In these applications, ink is deposited onto the high gloss cast coat finish in order to create ink images for graphic reproductions.
The use of a heated polished mirror-like finished roller for achieving high gloss finishes to a printed surface, as a separate application, off-line after the printing process and after the inks and coating have been thoroughly dried is also well known in the printing industry. The equipment used for the above application is manufactured by Matsumoto Kikai Manufacturing Company, Ltd., Tokyo, Japan and Billhoefer, N.J., U.S.A.
Aqueous coating compositions of a resinous thermoplastic coating material (clearcoat) such as thermoplastic, (meth)acrylic or (meth)acrylic-styrene copolymer or related copolymers in the form of emulsions are well known in the printing industry and presently are being used to coat inked and uninked layers during wet-trap in-line, off-line dry-trap, gravure, offset, silk-screen, flexography and related printing or coating processes.
The prior art printing methods which utilize aqueous coatings are disadvantaged in the gloss values which can be obtained. At the same time, the demand for high gloss graphics is rapidly growing, especially for use in magazine covers, packaging materials, paperback books and labels, among numerous other end use applications. At present, the use of UV curable and electron beam curable coatings, among others, are used in high gloss applications to meet the needs of the industry. These methods suffer from the disadvantage that the coating must be cured upon deposition, creating time constraints in manufacturing with a resulting compromise in productivity. In addition, the monomers which are used in these applications to create coatings tend to be hazardous and raise serious health and environmental issues in their continued use. In addition to other negatives, these methods are often very costly compared to aqueous coating methods. In addition to inline single coating units, expensive methods such as inline double coating units are also offered by a numerous printing press manufacturers in an effort to achieve high end results from inline wet or dry trap printing methods.
Today's demand for higher gloss graphics such as magazine covers, packaging materials, paperback books and labels, among other applications, is rapidly growing and represents a tremendous commercial opportunity. Printing press manufacturers such as KBA-Planeta, Komori, M. A. N. Roland, Mitsubishi, Heidelberg and Bobst, offer new press equipment with inline coating units allowing for wet or dry trap coating applications.
Coating materials employed for the above applications include aqueous based, U.V. curable and electron beam curable coatings (both aqueous and non-aqueous based), among others. In additon to inline single coating units, expensive methods such as inline double coating units are also offered by the above printing press manufacturers in an attempt to achieve high end results for inline wet or dry trap coating processes. Notwithstanding the technical efforts made by the press manufacturers, aqueous coating based processes prior to the present invention, provided lower levels of gloss compared to other printing methods.